Biphenyl purification process by plural stage fractional distillation

ABSTRACT

A METHOS IS DISCLOSED FOR RECOVERING A PIPHENYL STREAM FOR RECIRCULATION TO A HYDRODEALKYLATION PROCESS FOR PRODUCING BENZENE WHICH INVOLVES FRACTIONATING THE PRODUCT STREAM AFTER THE REMOVAL OF THE BENZENE TO PRODUCE A C9   AROMATICS CUT, A C10 AROMATICS CUT , A FUEL OIL CUT AND A BIPHENYL STREAM OF ABOUT 88 PERCENT PURITY.

R. M. BELLINGE'R ETAL BIPHENYL PURIFICATION PROCESS BY PLURAL Oct. 24, 1972 3,700,566

' STAGE FRACTIQNAL DISTILLATION Filed Oct. 13. 1969 i/zmIntm F fl 9 Um n 04 mm INVENTORS R. M. BELLJNGER J.T. CABBAGE A T TORNE V5 United States Patent Ofice 3 700 566 B'IPHENYL PURIFICA'TIOhI PROCESS BY PLURAL STAGE FRACTIONAL DISTILLATION Robert M. Bellinger, Bartlesville, kla., and John T.

3,700,566 Patented Oct. 24, 1972 ing which illustrates schematically one embodiment of this invention.

Referring now to the attached drawing, there is shown a feed stream being introduced through conduit 1 into Cabbage, Guayama, Puerto Rico, assignors to Phillips actioiiatol P tr leu Company Fractionator 30 comprises a tower containing a suit- Filed Oct. 13, 1969, Ser. No. 865,650 able number of trays. It is operated at a bottoms tower Int. Cl. C07c 7/04, 3/58 condition of about 522 F. and p.s.i.g. and a top tower US. Cl. 203-1 4 Claims condition of about 358 F. and 6 p.s.i.g.

10 The overhead from the tower is removed through con- ABSTRACT OF THE DISCLOSURE 17 to ovgrhead condenser 31, into accumulator 32. e ux is intro need from accumulator 32 throu h conduit A mFthOd dlsclosed for recovemig a blphenyl stream 20 into tower 30. From reflux accumulator 3% there is for recirculatlon to a hydrodealkylation process for prorecovered thmu h cond 21 c t M f bl d ducing benzene which involves fractionating the product in i to F1 th a 9 cu Sm e en stream after the removal of the benzene to produce a C g n mo r ow rough product conduit 21 1S controlled by liquid level controller 33 on accumulator 32. aromatics cut, a C aromatics cut, a fuel 011 cut and a bi- The reflux rat t th t w th h d phenyl stream of about 88 percent purity. e o e 0 er mug con 15 trolled by flow controller 34. From a trap tray of tower 30, there is withdrawn a This invention pertains to the production of benzene. 20 Stream through conduit 35 t0 Separating drum Over In one of its more specific aspects, this invention perhead gases from the drum pass back into tower 30 through tains to the production of benzene by the hydrodealkyla- Conduit 37 While a 10 aromatic cllt is Withdrawn through ti of t l conduit 16 to disposal, e.g., gasoline blending.

That process of r d i benzene b h h d d A second sidestream is withdrawn from the tower alkylation of toluene is well known. Generally, it involves gh conduit 9. One Portion of this S a is re ntrocontacting toluene with hydrogen under conditions which duced into towel" through Conduit and a Second P produce benzene in a stream from which it is'recovered. tion is transferred through Conduit 11 t0 he aft r-dis- This latter stream, after the separation of benzene and cussed p y pp one the other of low 011- lighter materials, toluene and xylenes, is processed to protroiiers 39 and Positioned n Conduits 10 and 11 reduce a C and lighter cut, a C aromatics cut, both suit- 30 p y, Operate in conjunction with a liquid controller able in color and other properties for direct blending into 41 on the draw-0ft y to regulate the flow through one motor fuel, a residual fuel cut, and a biphenyl cut for r e th r of he conduits. recycling to benzene production. The method of this in- From the bottom of towel there is circulated a vention is di t d t thi l tt processing stream through conduits 5 and 6 to reboiler 42. A second According to this method there is provided a process stream, withdrawn from a trap tray just above the refor recovering a stream comprising biphenyl from a hyboiler section of the tower, passes through conduit 8, the drodealkylation process efliuent stream from which bentWO Streams being Combined and introduced i to the r zene and lighter materials, toluene and xylene have been boiief through Conduit 3 d aving the reboiler and removed, which comprises introducing said stream into a entering h tower through conduit A Portion of that first fractionation zone, withdrawing from the fractiona- Stream wlthdl'tiwli h q conduit 5 is ut d to fu l tion zone at a point of highest biphenyl concentration, a thfqugh P i 7, ilquld lfl'el controller 43 Operating in biphenyl-containing stream, introducing this stream into a conlllilctioil With a temperature Contfoiief to regulate the second fractionating zone from which there is separated amount 80 routed t0 fuelan overhead stream which is introduced into the first The q y of flow through conduit 6 is controlled y fractionation zone and a bottoms stream comprising biflow controller 44 in conduit 6 and the amount of flow phenyl. through conduit 8 is controlled by level controller 45 In Accordingly, it is an object of this invention to provide relation to the level on the draw-off tray. The temperature a process for recovering a suitable gasoline blending comof the reboiler efiiuent returned to the tower through conponent from a hydrodealkylation process. duit 4 is controlled by liquid level controller 46 operating It is another object of this process to recover a biphenyl in conjunction with proportional flow controller 47 in fuel stream of optimum composition for recycling to a regas conduit 48 to the reboiler, this flow controller valve action zone of the hydrodealkylation process for the probeing positioned in relation to the flow through conduit 8. duction of benzene. Quantities and analyses of the various streams con- The method of this invention will be more easily undercerned in the operation of fractionator 30 are shown in stood if explained in conjunction with the attached draw- Table I.

TABLE I Blphenyl C0 10 stripper Reboiler Fuel Feed aromatics aromatics feed tee oil ggriduit 1 21 1e 11 3 7 Rate. b. .h 125 66 33 35 220 6 ciiiifiifitfiffl 4s 42 6 2 53 0 l-methyl 3-ethy1benzen 940 717 213 66 1, 074 8 1,2,4-trimethylbenzene- 1, 086 709 364 1, 249 10 1,2,3-trimethylbenzene 180 96 81 16 210 2 1,3-methyl-5-ethylbenzene.- 72 14 56 9 87 1 1,2,3,5-methylbenzene 72 1 (i6 20 93 1 Napthalene 11 0 4 12 16 0 Biphenyl 455 0 5 584 1, 37 4-methylbiphenyl. 45 0 0 47 199 s Fluorene 51 0 0 4 767 47 Anthracene 40 0 0 0 416 30 Total s, 000 1, 579 795 845 5,289 154 Of that quantity of about 113 b.p.h. taken as a side out from fractionator 30 through conduit 9, about 35 b.p.h. is introduced into biphenyl stripper 38, the balance being returned to fractionator 30 on the tray beneath the draw-off tray.

(c) introducing said second lower side stream into a second fractionation zone;

(d) recovering from said second fractionation zone an overhead stream and a bottoms fraction comprising biphenyl;

The biphenyl strlpper 1s a tray-containing tower, the (e) introducing 1nto said first fractlonatron zone said liquid charge through conduit 11 being introduced on the overhead stream from said second fractionation zone uppermost tray. The tower is operated at a bottoms tower in accordance with step (a); and, condition of 540 F. at about 10 p.s.i.g. (f) withdrawing at least a first stream from said first From the bottoms f the p y pp a Stream is fractionation zone, dividing the fuel oil bottoms frac- Withdfawn through Conduit a Portion being introduced tion into two portions, one of said portions constitutthrough conduit 14 t0 reboiler 49 and back 110 stripper 38 ing a econd tream passing aid first and second y y of Conduit 18, and a Portion being recovered to streams through a reboiler and into said first fraca benzene Producing PromSS {brough conduit The tionation zone, the first stream being withdrawn from amount so routed to recovery rs controlled by tempera- 15 a trap tray positioned above the lower extremity of ture controller 50 relatrng to flow controller 51 in con- Said first fractionation Zone and the second Stream duit 15.

In conjunction therewith, liquid level controller 52, opbang wlthdrziwn from slibstagnany the lower ex t th b U f th t r t 1 th f l to tremrty of said first fractionation zone, the rate at era {Hg e o Om 0 e Owe con m e which said first stream is withdrawn being controlled reboller 49, with the result that under stabrlrzed operab H uidlevelon said Ha Ha tion, that quantity of material returned from the reboiler 2 1; q thod f 1 p fired through conduit 18 to the tower is about 50 percent f y 1 re .5 vaporized, the reboiler circulation rate being about 45 Y He gas an t e me 0 ue gas Sal re 01 er bp'h is controlled by the rate of withdrawal of sa1d first stream An overhead stream from the biphenyl stripper 38 is from Sald trap taken through conduit 12 at the rate of about 16 b.p.h. T Q 2 Whlch the P0111011 This material is introduced into fractionator above the of 531d two PortionS 1S removed as a fuel 011 Product stream drawn off through conduit 9 from the trap tray. Stream- Stream analyses around the biphenyl stripper 38 are 4. The method of claim 3 in which the rate at which shown in Table II. 30 said fuel oil product stream is removed is controlled by TABLE II Biphenyl stripper Stripper Reboiler Biphenyl teed overhead tee product Stream:

Conduit 11 12 14 15 Rate, b.p.h as 16 20 Compouents, b.p.h.

0rthoxylene. 2 2 0 0 1-methyl-3-ethylbenzene 66 64 5 2 1,2,4-trimethylbenzene.-. 85 82 6 3 1,2,3-trimethylbenzene. 16 15 2 1 l,3-methyl-5-ethylbenzene 9 8 2 1 1,2,3,5-methylbenzene. 20 16 8 4 12 5 15 7 Anthraeene.. 0 0 0 0 Total 845 373 1,087 47 It will be seen from the above tables that approximatethe temperature in the lower extremity of said first fracly 91 percent of the biphenyl in the original stream is re- 50 tionation zone. covered in a stream of about 88 percent purity. It will be References Cited further seen that the C aromatic fraction is substantially UNITED STATES PATENTS devoid of the aromatics of naphthalene and heavier while the C aromatic fraction is essentially void of naph- 3,210,271 10/1965 Byerly et 203 82 thalene and biphenyl. Furthermore, there is produced a 3297566 1/1967 Moyer et 203 82 3,309,288 3/1967 Butterbaugh 2032 minimal quantity of fuel 011. 3 3 4 It will be appreciated that various modifications can be Q33? 1 7/1967 Thefleg et made to the method of this invention in light of the above 24 9/1968 hues 203 84 disclosure. Such, however, are considered as being within 35,084 3/1969 Cabbage et 260 672 3,494,861 2/1970 Munro 203-82 the scope of the rnventron.

,What is claimed is: 3,310,594 3/ 1967 Peterson et a]. 260-672 1. A process for producing a biphenyl product from 3296323 1/1967 Myers et 260672 the hydrodealkylation unit eifiuent from which benzene 3 223 5 2 Bauer 260-68348 and lighter materials and toluene and xylene have been gag :3 1 g at 260 672 substantially removed, said efiluent comprising C aro- 12/ 9 5 avlson 260672 matics, fuel oil, C aromatics and biphenyl, which comprises: OTHER REFERENCES (a) introducing said efiluent and an after-defined over- FOWle & Pitts, Thermal y q y Chemhead stream into a first fractionation zone; Progress, VOL PP- 37-40 P (b) removing from said first fractionation zone an overhead fraction comprising substantially C aro- WILBUR BASCOMB Prlmary Exammel' matics, a bottoms fraction comprising substantially S 1 R fuel oil, a first upper side stream comprising C aromatics and a second lower side stream comprising 260-672 674 biphenyl; 

